A city firefighter rescued two men who were left stranded about 100 feet in the air today after their mobile scaffolding unit stalled as they worked on a Queens building, authorities said.

The workers were toiling on a shuttered New York Power Authority facility on 20th Avenue near 31st Street in Astoria around 1:45 p.m. when the motor of their SkyClimber machine stopped running, fire officials and a NYPA spokesman said.

The FDNY responded and lowered Firefighter John Friedrich from the roof in a daring rescue attempt.

Friedrich, from Squad 228 of Special Operations Command, attached rope tethers and harnesses to both men, who were then separately raised to the roof, said a fire department spokesman. Neither man was injured, officials added.